1. Field of the Invention
The present invention relates to a manufacturing method of an optical device provided with a resin thin film having a micro-asperity pattern.
2. Background Art
In this specification, “optical device” is a device which has at least a micro-asperity pattern on its surface and diffuses, condenses and reflects light, “micro-asperity pattern” is a generic term of asperity shapes that develop one-dimensionally or two-dimensionally and are 0.1 μm to hundreds of micrometers in depth and arbitrary in width, length and shape. In addition, “electronic device” is a generic term of electronic circuit constitutions for displaying pixels comprising pixel driving elements such as thin film transistors (TFTs), metal wiring contacts or the like.
Recently, as a liquid crystal display such as a personal computer, a TV, a word processor, a video equipment or the like, reflection-type liquid crystal display that displays a liquid crystal image by reflecting external light instead of using a backlight has been developed in order to increase the functionality and reduce the size, power consumption, cost or the like.
As shown in FIG. 17, a reflection plate 1 which is used in the above reflection-type liquid crystal display is used to increase the viewing angle of the image display of the liquid crystal display by diffuse-reflecting light coming from a counter substrate 28 with a micro-asperity pattern.
As shown in FIG. 18, the reflection plate is provided with an electronic device such as a thin film transistor or a wiring contact 31 under a resin thin film 4, and a contact hole 37 is formed for penetrating the resin thin film 4 for providing electric connection.
As a manufacturing method of such reflection plate, there is disclosed a method in which a photosensitive resin material applied by spin coating or the like onto a surface of a substrate made of glass or a resin is softened or melted, a micro-asperity pattern is formed by pressing a die having the desired micro-asperity pattern, and the asperity patterned shape is processed by photolithography to form a through-hole which penetrates the photosensitive material.
According to the conventional method, since a temperature when the micro-asperity pattern is formed is controlled so as to be lower than a photosensitivity extinction temperature of the photosensitive resin material, a contact hole can be formed by photolithography. However, in this conventional method, when ultraviolet rays and the like are applied with a mask in photolithography, since the rays are diffused in the photosensitive resin material because of the micro-asperity pattern formed on the surface of the photosensitive material, there are problems such that 1) an exposed region is blurred and processing precision is lowered and 2) an exposed amount becomes uneven and a development defect is generated.